The subject matter disclosed herein relates to dynamic windows, such as smart windows. More particularly, the subject matter disclosed herein relates to a technique for making electrical contact to a dynamic window, such as a dynamic Insulated Glass Unit (IGU) window assembly.
For a conventional dynamic IGU, the transparent conducting layer of an electrochromic pane is semi-hermetically sealed within the IGU and electrical contact must be made between the transparent conducting layer and the exterior of the sealed IGU. Conventional techniques for making the electrical contact involve using a fired, silk screened or soldered bus bar. FIG. 1 depicts a conventional dynamic IGU 100 in which a bus bar 101 runs underneath a seal 102 in order to provide an electrical connection to an Electrochromic (EC) coating layer 103. Bus bar 101 creates an electrical contact path to a top conducting layer (not indicated) formed on EC coating layer 103. The electrical path is completed through the stack of the electrochromic device to a bottom conductive layer 104 and then to a second bus bar 105 that is outside seal 102. Second bus bar 105 is connected back to a voltage source 106. Bus bar 101 allows an electrical contact to be made to the top of EC coating layer 103 from outside the sealed volume of IGU 100. EC coating layer 103 is too delicate for seal 102 to be attached directly to EC coating layer 103 so EC coating layer 103 cannot extend underneath and be available for electrical contact.
The breaching of seal 102 by bus bar 101 reduces the reliability of seal 102. FIG. 2 is a Pareto chart depicting a typical EC Absorptive Window Failure Mode Effects Analysis (FEMA) in a finished IGU product. FIG. 2 shows that failure of the primary seal at the bus bar is one of the highest risk reliability failure modes in a finished IGU product. Accordingly, if the breaching of the seal by the bus bar could be eliminated, one of the highest risk reliability failure modes in a finished IGU product could be eliminated.